“American Bridge 21st Century or AB PAC is a liberal American Super PAC that supports Democratic candidates and opposes Republican candidates. It was founded by David Brock in 2010 and is associated with Media Matters for America.”
https://en.m.wikipedia.org/wiki/American_Bridge_21st_Century
So sad Brock was one of the few great conservatives who transformed to a traitor.
As did Ariana Huffingnpuffington, later.